It is proposed to establish the Washington University Small Animal Imaging Resource (WUSAIR) to provide state-of-the-art facilities and infrastructure for magnetic resonance imaging (MRI) and positron emission tomography (PET) analysis of mice, rats and other small laboratory animals. Located in the heart of Washington University Medical Center in St. Louis, WUSAIR will combine instrumental and intellectual capabilities found at few other institutions. WUSAIR will serve a broad community of scientists non-expert in MRI or PET technology who have a pressing need for quantitative image analysis of small laboratory animal model systems. A particular focus will be on mice and rat models of cancer. WUSAIR will also continue research and development at the frontier of imaging technology in an effort to make the most powerful of the new imaging strategies available to its community of users. Purchase of new PET and/or MRI scanners is not requested herein. Indeed, Washington University has generously supported the recent acquisition of such equipment as part of its continuing and substantive commitment to basic biomedical research. Currently on site and fully operation in the Imaging Research Center are two Varian INOVA 4.7 T MRI/MRS small animal research scanners. A PET scanner dedicated to small animal research, the microPET, will be delivered and sited in the Clinical Sciences Research Building early next year. These PET and MRI small animal research scanners will form the core instrumentation of WUSAIR.